Mix together the olive oil, garlic powder, smoked paprika, salt, and pepper.
Brush the chicken breasts with the sauce.
Heat a skillet over medium-high heat and cook the chicken for 6–7 minutes per side until cooked through.
Let it rest 5 minutes, then chop it into bite-sized pieces.
Whisk together all the ranch dressing ingredients in a small bowl. Taste and adjust for seasoning.
Brush the cut side of the focaccia halves with oil, and toast them cut-side up in a dry skillet or under the broiler for 1-2 minutes, until golden.
Preheat the oven to 400 F.
Line a rimmed baking sheet with parchment.
Arrange the bacon in a single layer. Bake for 15–18 minutes until crispy. Transfer to a paper towel-lined plate and set aside.
Spread the ranch dressing generously on both cut sides of each focaccia portion.
Layer the bottom half with iceberg lettuce.
Add the tomatoes.
Add the avocado.
Add the chopped chicken.
Add the purple onion.
Layer on the bacon.
Top with the hard-boiled egg slices and crumbled blue cheese.
Close with the top half of the focaccia.
Cut the sandwich into four parts, or as many as needed; to make it easier to cut, you can wrap it in parchment paper or plastic wrap. Serve the loaded Cobb sandwiches immediately.